A perovskite oxide dielectric such as paraelectric strontium titanate (SrTiO3, referred to as STO hereinafter) thin film and ferroelectric barium strontium titanate ((Ba, Sr)TiO3 referred to as BST hereinafter) thin film is high in dielectric constant as compared with a silicon oxide (SiO2) thin film, a silicon nitride (Si3N4) thin film, and a tallium oxide (Ta2O5) thin film which have been conventionally used as an IC dielectric thin film capacitor, so that it is expected as a preferable dielectric material to reduce the area of the IC dielectric thin film capacitor.
As a method for forming an oxide dielectric such as the perovskite oxide dielectric thin film, while a sputtering method, a CVD (Chemical Vapor Deposition) method or the like is used, it is necessary to perform an oxidizing process and a crystallizing process in atmosphere containing oxygen at high temperature in any method in order to obtain a high dielectric constant. Therefore, the bottom electrode and the top electrode sandwiching the dielectric thin film are conventionally made of a material which is high in heat resistance and is not likely to be oxidized, or an oxide conductive material which has conductivity even when oxidized. For example, Pt, Ir, and Ru have been used.
Among them, Pt is most widely and generally used as the electrode material because it is high in heat resistance and hardly oxidized. However, since Pt is high in catalytic ability for a reduction reaction, the perovskite oxide dielectric is reduced in the process of producing the capacitor, and its characteristics problematically deteriorate. Especially, when Pt is used in the top electrode, the effect is considerably problematic, and the top electrode material not causing deterioration in characteristics is required.
Thus, as the top electrode material to replace Pt, a capacitor using an electrode containing oxygen, or an iridium oxide serving as an oxide conductive material is proposed to be used in a ferroelectric memory mainly.
For example, Patent Document 1 discloses an example in which a top electrode including platinum, iridium, and ruthenium containing oxygen of 1020 atm/cm3 or more is formed on an oxide dielectric film including lead zirconate titanate (PZT).
In addition, Patent Document 2 discloses a ferroelectric capacitor including a top electrode having a layered structure including a first conductive film made of an iridium oxide and a second conductive layer made of Pt or Ir.
Patent Document 1: Japanese Unexamined Patent Publication No. 11-251523
Patent Document 2: Japanese Unexamined Patent Publication No. 2006-222227